Generally, a patient suffered from injured portion of spinal bones does not carry himself or herself in such a state. Even though a patient having a weak damage acts, the damaged spinal bone compresses adjacent spinal bone or comes into contact with adjacent spinal bone, thereby causing a pain in the patient. In addition, although the patient is placed under medical care, the recovery is delayed.
Therefore, the patient suffered from the ruptured or damaged spinal bone has a surgical operation on the adjacent spinal bones by supporting the damage spinal bone with an artificial prosthetic device so as to prevent the damaged spinal bone from being pressed or expanded.
Such an artificial prosthetic device consists of pedicle screws inserted into upper and lower portions of the damaged spinal bone to serve as a fixation, and a rod engaged to the pedicle screw to serve as a support.
FIG. 7 illustrates the structure of a conventional artificial prosthetic device.
Referring to FIG. 7, a pedicle screw 30 has an opening 32 formed on an upper portion of a head engaging groove 31, and a threaded portion 34 formed on inner surfaces or outer surfaces of support walls 33 provided on both sides of the opening. The support pipe 36 of an engaging member 35 is placed on the outer surface of the support wall 33, and then, a male threaded part 37 is threadedly engaged with the threaded portion. With the above arrangement, there is a problem in that a rod 20 is not horizontally placed. In addition, in case the rod 20 is inserted at an inclined angle, the rod 20 should be pressed against the head engaging groove 31 by using a separate guide tool, so that the engaging member 35 can be engaged to the pedicle screw by means of a screw and a ring or a cap.
More specifically, the rod 20 should be forcibly held in the engaging groove 31 by using the separate guide tool before the male threaded part 37 of the engaging member 35 is threadedly engaged with the threaded portion of the engaging groove 31. In addition, the rod can be pre-engaged by the male threaded part 37. As such, the weak fastening force of the threaded portion of the support wall can be complemented by the screw, the outer ring or the cap used on the outer portion of the engaging member. Since the use of the outer ring or cap increases a width of the engaging member, it may cause the interference between the components in a narrow space on the operation.